The number of available phone numbers with a 740 area code will run out next year, so Ohio is introducing 220.

The Public Utility Commission of Ohio is preparing people living in southeastern and central Ohio for the change by asking people to practice dialing all 10 digits starting Sept. 20. Here are answers to a few questions you might have about the change.

Why is this change necessary?

The North American Numbering Plan Administrator, which distributes area codes across the United States, informed PUCO that the 740 area code would run out by mid-2015.

PUCO asked people in the 740 area code whether they would prefer an overlay — everyone must dial 10 digits for local calls but only new customers would be assigned the new area code, 220 — or a split — half the 740 area code customers would receive a new area code and everyone would retain seven-digit dialing on local calls.